Apparatus for classifying articles by color



Filed Dec. 29, 1949 y 8, 1954 w. JACOBSON 2,678,725

APPARATUS FOR CLASSIFYING ARTICLES BY COLOR 2 Sheets-Sheet l Flgj. Z

Invenbcr: WoodrOw R'Jacobson,

Hls Attorney.

y 18, 1954 w. R. JACOBSON APPARATUS FOR CLASSIFYING ARTICLES BY COLOR Filed Dec. 29, 1949 2 SheetsSheet 2 550 WA VEL ENG m- MILL/MICRONS 0 0 0 O 5 4 M M 1 N02 Show JKMM lnvehoorz Woodrow R.Jacobson,

His Abbow ney.

Patented May 18, 1954 Armmrmsr n S FY NQ RT Q ES:

' BY ooLo t Woodrow R. Jacobson, Schenectady, N, Y., as-

s'ig'xio'r' "to *General'Electric- Company, a corporaf' a g witn ss 949, SeriaLNo.1.35;?82

' 1 ect of h v ptiq s matic means for quicklfi" and ci' articlesliy color."

Dolor classification comprises two iactors: hromatic'ityj and b ightri" ""Chrdrh tici't'y refe'rs tothe redness of fineness ofth''arti'c1s;'and brightness refers to itsliglitri'ess"or darkness, This invention p'rovidesiofthe"sorting oi articles to proyide autoe sicanr or in i according westerns-s catiofihas ed upon chfoilna'ticltyjah d tightness. "Otheroijjects 'and'advafitages will appear as thefdescriptionproceds. The 'fatiiresoiithe in- Vhtiiiil' which are 'belived't'o' be novel and patentable are pointed out in thc'l i nsftrhibhiorm a part (if this" specificaitioflf I For 'a better understanding of the invention,

rei'ere'nce'is fnadein thefollowing descrip'tio'nto the accompan ing d awing,in which Fig"."1 is a schematic view, partly iii' section; of apparatus embodying principles of thisin'i'rention; Fig; -2" is a; plan view are rotary shutter used "ifl" the'Fig. '1 apparatus and Fi'gi"3 is "a spectrophotometric CiiIV'e O f'a' cigar.

Referringnow to Fig. 1, an electric lamp I, a animating lens' Land a pair of 'beam=forming slits 3 provide two beams of light represn'tedby broken lines in the drawing? The intensities ofthese twobe'ams aremodulatedin phase op": position by a rotary shuttefdfliivenbyan electric'motor t'throughshaft 6T andgears 1;

Referring now to Fig: 2 ,which is-a p'lan View of. rotary shutter "4, the broken circles '8 and 9 represent cross sections ofrthe two beams of light; Shutter 4 may comprise'threeblades; as shown, and may be rotatedat a speed 01518.00 "R. H. M;; for example. The shutter intensity modulates eachoi the light beamsat a frequencfi of 90' cycles per'secon'd. The'two beams are'modulated in phase-oppmitiofi" toeah other: that" is, when one beam is coinp other"b'eam is computes "transmitted? ists -i r ims iii Fi -'1 sl t?? he th? ee s? asses. th u h a: htl i v d m f h i reri i m qr i i ffi s .t l Th we lie enso a d u ms' 3 t. the'tiiro'b'eamsi "This attenua r t. i em ie ietel 'tut d rty the shutter; the

" i ea qnl 6 Claims. (01. 209-111) 2 type which comprises alarge disc of polarizing meta-min; andtrifsmallrfdiscs of polarizing niatrial l'2 and E3. The s'i'rlall discs l2 and="l3' are placed in respective light beanie" with their; respective axes of polarization perpendicular-to ea'ciipther. "For ex'ar'nj'p ',dis'c' aa'may t e-p9 1: tiotjole'd for maximuintransrnissiion *ofli'ght' which is "polarizedin a directionperpendiciilar to the plane of the drawing; and di'scit'may bepositioned 'for"iriaximumftransmissibn of light which i's'pola'rized in direction parallel to the plane of theidfawmgifl i The large polarizing disc II is positioned in both beams. When'the polarizing axisjof'disc H 15 is parallel: to the polarizing" axis'of'disc l2,'-'the maximumamount O'flighti s"transmitted in the integrating sphere"'2 L cilitate the attachment of Eart offtl'ie reflected lightcollected by the inr'riit'ted intheright-handbeam'fand' the minimum amount in the left-hand"bam.""Adjustmerit of disc"! I to an? intermediate "position provides" a corresponding intermediate"adjustment of the relative intensities-ofthetwolight beams. "adjustment kiiob'd'' andgears I5 maybe providedidr adjusting'theposition of disc H:

The two beams next pass through twocolor filters I'S' 'and"1"!:; respectively, to provide "two beams of'different'colors'."Filter [6 may be blue a'nd'filter l1; may be red;'' for exampler- "Thenth'e beams passthrough prismaticiens es i8'and i9; respectively, and are therebydirected to an article tobe'sorted, 20; which may he a'cigar.

"L'ightrefiected by'th'e 'cigarfiscollected by an This is a substantially spherical enclosure having a whitedifiusing inner surface, so that the entirevolume-within the sphere isat substantially the sarne brightn'ess; *The brightness Within the sphere depends upon the totalamount of-light reflected by "cigar 23. Operation of the integrating sphere is not substantially affected by the fact that portions of thesphere may befiat, as illustrated, to faother apparatus;

tegr'ating sphere passes through an opening -22 to first photoelectric means; which maycomprise a'phototube 23', asourceoi directvoltage- 24,- and load r's'istor25. Thisfirstphotoelectric means is responsive" to bothcolo'r's 'of iijghtrefiectedty the "cigarifl; and since tlie'se"clors' alternate in time difference averageinten'sity or the cted li htproduce'san "alter"- t'r'i'c curren conducted time ti ii i i 'i fs'ti iii "whis ifl etq the On the other side of the integrating sphere, part of the reflected light passes through an opening to second photoelectric means, which may comprise a color filter 21, a phototube 28, a source of direct voltage 29, and a load resistor Filter 2'! preferably is the same color as filter i5, and has substantially zero transmission in the region of the spectrum where filter ll transmits. Hence it transmits only blue light. Therefore, the second photoelectric means is responsive to one color only of the reflected light.

The light which is reflected by mirror |0 passes through an attenuator comprising a fixed polarizing disc 3! and a rotatable polarizing disc 32. The amount of light transmitted through this attenuator is adjustable by adjusting the position of disc 32 to bring the polarizing axes of the two discs nearer to or farther from parallelism. An adjusting knob 33 and gears 34 are provided for adjusting the position of disc 32.

The light which passes through disc 32 is transmitted through a light-conducting tube 35, which may be made of Lucite, or may be a system of mirrors or reflecting prisms, for example. The light emerges from tube 35 at end 36, is then reflected by a mirror 3'! to phototube 28. Thus a reference value of light from the right-hand beam is transmitted to phototube 28; while the amount of light from the left-hand beam which reaches this phototube depends upon the amount of such light reflected by cigar 20. Since the two beams are intensity-modulated in phase opposition, an alternating current is provided through resistor 38 which depends in magnitude and phase upon the average intensity of light of a single color reflected by cigar 20.

As is hereinafter more fully explained, the value of alternating current through resistor 25 corresponds to the chromaticity of the cigar, and the value of alternating current through resistor 3i) corresponds to the brightness of the cigar. These currents produce alternating voltages across resistors 25 and 35, which are amplified by amplifiers 38 and 39, respectively, and are then applied through transformers tive rectifier bridges 42 and 43 comprising a part of a classifying means hereinafter described.

Connected to motor 5, and rotated thereby, is a small alternator 44 which generates alternating current having the same frequency as the intencity-modulation of the light beams provided by shutter 4: 90 cycles per second, for example. This alternating current is transmitted through transformer 45 to phase-sensitive rectifier bridges 42 and 43. Preferably, the voltage across the secondary of transformer 45 is considerably larger than the maximum voltage to be obtained across the secondary of transformer or the secondary of transformer 4|.

The secondaries of transformers 4|], 4|, and are each provided with a center tap. The output voltage of rectifier bridge 42 is obtained between the secondary center tap of transformer 40 and the secondary center tap of transformer 45. When no current is applied to the primary of transformer 40, this output voltage is zero. When a current is applied to transformer 40 which is in-phase with the current applied to the primary of transformer 45, the output voltage is positive; and when the two currents are out-of-phase, the output voltage is negative. In a similar manner, the output voltage of rectifier bridge 43 is obtained between the secondary center tap of transformer 4| and the secondary center tap of transformer 45. Values of these two output voltages 4|] and 4| to phase-sensiother article, and control sorting equipment through electronic switches likewise comprising part of the aforementioned classifying means.

The classifying means also includes a first elec tronic switch which may comprise vacuum tubes 15, 47, 48, and 49, having anodes connected in series with energizing coils of relays 55, 5|, 52, and 53, respectively. The vacuum tubes 46-45 have control electrodes connected together and to the secondary center-tap of transformer 40; and have cathodes connected to different points on a voltage divider 54 connected across a direct voltage source 55, as shown; so that the cathodes are maintained at diiferent potentials, and the tubes have difierent values of bias voltage between their respective cathodes and control electrodes.

lhese bias voltages may have values such that when the output of rectifier bridge 42 is zero, tubes 46 and 41 are conductive and relays 50 and are energized, while tubes 48 and 49 are nonconductive and relays 52 and 53 are de-energized. When rectifier bridge 42 provides a positive output voltage, the negative bias of tubes 48 and 49 is decreased, and at a selected value of such output voltage tube 48 becomes conductive and relay 52 is energized. At a larger value of positive output voltage, tube 49 becomes conductive and relay 53 is energized. At a selected value of negative output voltage from rectifier bridge 42, tube 47 becomes nonconductive and relay 5| is tie-energized, and at a larger negative value, tube 45 becomes non-conductive and relay 5!? is de-energized. The various states of the relays thus correspond to five chromaticity classifications, and the relays may operate suitable sorting machinery to sort the articles classified into chromaticity groups.

The classifying means also second electronic switch which comprises vacuum tubes 56, 51, 58, and 59, having anodes c0nnected in series with energizing coils of relays 65, 5|, E2, and 53, respectively. The control electrodes of tubes 56-59 are connected together and to the secondary center-tap of transformer 4|, and their cathodes are connected to different points on a voltage divider 64 connected across a direct voltage supply 65. Operation of the second electronic switch is similar to that of the first switch, except that the relays of the second switch may operate sorting machinery to sort the articles into five groups of diiferent brightness. Thus, under the combined control of the two electronic switches, the articles are sorted into 25 different groups corresponding to the 25 possible combinations of five classes of brightness and five classes of chromaticity. It will be appreciated that other numbers of groups may be used. For example, in sorting cigars only nine groups corresponding to three classes of chromaticity and three classes of brightness are gener ally satisfactory. A change in the number of groups requires only a change in the number of elements in the electronic swtiches.

Referring now to Fig. 3, curve 65 represents a typical spectrophotometric curve of a cigar, which shows the percentage of light of various wavelengths reflected by the cigar. Such a curve may be made by a spectrophotometer. Dotted curves 5? and 68 represent the transmission characteristics of filters l6 and I1, respectively. The transmission characteristic of filter 21 is preferably the same as that of filter l6, and hence is also represented by curve 61.

further includes a ference" may=haveza certain value for cigarsof: average chroma-ticity, which shouldzbe. sorted into.

the. middle group of; the; chromaticity classification; and. cigars; for which. the. difference in, re-

flection at these two colors is substantially greater orless than; this; average value. shouldbe. sortedz,

into-other groups.

The selection otthe: two: wavelengths, used: to, determine the chromaticity-ofranobject can. best be made by analysisof spectrophotom-etric:curves. of}. the objects. to. be-v of representative. samples sorted. Thatiis;representative samples of'the ob.- iects; such as cigars, aresorted according totheir appearance to. the eye, and speotrophotometriocurves are. made with, a spectrophotometer: of" each: object; in. the sample. These will: be curves. similar to curve 667. for cigars. Then bycomparison of: the curves: so obtained with thesorting of the; objects: by appearance, that portion of the curves: is; selected which varies in average slope most markedly incorrespondence: with: variations in color apparentto the eye. The best pairof wavelengths-to usein sorting are those at re.- sp-ective: ends of: the. portion of the: spectrophoto.- metric curves so selected For example, in. color sorting of cigars, best. color diiTer-entiation. can be obtained: with color filters; having. maximum transmissionat 5100=and 620 millimicrons, respectively, as. illustrated. by curves: 6.1; and 68; Fig. 3;; while in color sorting of lemons, best results are obtained with filters having maximum trans.- mission at 550 and 675 millimicrons. respectively.

brightness of the cigar is. represented by the'distance of curve 6'6 above the; horizontal axis. Thus, different brightness values, chromaticity: being the same, would be represented by similar curves having a fixed vertical separation from each other. Thus brightness may be determined; by measurements made at any one color. In the apparatus described, blue has been selected arbitrarily. A cigar of average brightness is selected; to establish the middle groupv of the brightness classification. Cigars. having substantially difierent brightness values. are sorted into. other groups.

Referring again torFi-g. 1,. the apparatus. preferably is adjusted with a cigar having average, chromaticity and average brightness. Polarizing disc i l is rotated to adjust the relative intensities; of the two light beams untilv the cigar of average chromaticity produces no alternatingcurrent through resistor 2-5, and hence zero output from phase-sensitive rectifier bridge 42. Disc 32; is rotated to adjust the amount orlight transmitted from the right-hand beam to phototube 28 until the cigar of average brightness produces no. alterhating current through resistor 30', hence. sero output of phase-sensitive rectifier bridge 43. Cigars having substantially these chromaticity and brightness values. will then always be sorted into the center group. The limits of each group into it ich the cigars are sorted can be adjusted by adjusting the taps on voltage dividers 54 and to which the cathodes of the various vacuum tubes are connected. This adjusts the bias voltage on these tubes, and adjusts the values of grid voltage, at which the respective tubes become conductive or nonconductive.

the. diiierenceim the intbti htness of lamps '1 variations. in; current; hrou h since: at wOrbfia -z. omparisons. s st m s; use

for. both-.- the; eh bmaticitnendi g-1. i tness-r classification-s;ca bration ofm beaann rat s l ve stable, @lId-liSiHQt! att sted-l by-moderateva i ti n Howeve ubs a tial'ichangaimtheg, 9191: temperatu e o light emittedr lost lam-n twil asset. the; calibration Thereiore; itrmagbei esirable czoperate-the lamp from a. liegulatedipower upply.- Howeven m ll the amnfilam nt are notzobieotionabic, sinceithecolorro v he light emitted; isaffected mu h z essr hanz. e b i tn s by such-.uariatiom.

will beeapnreciaterh that-thisinventionis not time: o 0. er. but i equal applicable to thee. tineiofitoth r articles-by o r; and may. alsozbeiused fon l Sui-cation; r. @0101" monitoring at products which must. be. ma tained; at uniform; colon. n r je tin 0191- fect ve-artioles, or toncortr lling a manufacturing' process to revent olor. ev ations. of: the prodgict.

Haring: described the; principles off his. invention and the best mode in which. I have, contem plated applyin those. princip es, wish it t b understood that. the examples described; are illustrative only, and"thatothen-rneans,,may be employed without. departing from; he rue ope f the; invention.

I. claim. asznew and: desire to se r y Letters; Patent: of; the United States; is:

1... Apparatus for classifying articles. by color, comprising. means. to promise-twili ht be m f different. colors; means to; direct. such beams to an: article tabeclassiiired; means.- for modulating the intensities of such beamsin phase opposition, an. integrating sphere to collect. substantially all light. reflected: by such article, photoelectric means responsive-to both. colors. of such collected light, whereby.- an alternating electric signal is. obtained which is. related to. the chromaticity of such article, and photoelectric means responsive toonlyone color oi such collected. light, whereby electric signal; is obtained; which is related to the brightness: of such article.

2. Apparatus for classifying articles by color, comprising means to. provide two light beams of different colors, means to. direct such beams to an article to be classified, means for modulating the intensities of such beams in phase opposition, means for adjusting the relative intensities of such beams, an integrating sphere to. collect substantially all light reflected by such article, first photoelectric means responsive to both colors or suchcollected light, whereby an alternating electric current is obtained which is related to. the ohromaticity of such article, second. photoelectric means. responsive to only. one color of such collected light, means to direct a reference value oi light to said second photoelectric means, such reference light being intensity modulated in phase opposition to the reflected light tov which said second photoelectric means responds, whereby an alternating electric current is obtained which is related to the brightness of such article,

classifying means responsive to each of said photoelectric means for classifying such articles into groups according tochromaticity and brightness classes corresponding tohselected values or" such electric currents.

3. Apparatus for classifying articles by color, comprising a light source which provides first and second light beams, a shutter for modulating the intensities of such light beams in phase opposition, an attenuator for adjusting the relative in-.

tensities of such light beams, color filters positioned in the two beams to transmit different colors in the respective beams, means to direct the two colored light beams to an article to be classified, an integrating sphere to collect su stantially all light reflected by such article, first photoelectric means responsive to both colors of such collected light, whereby an alternating electric current is provided which has an amplitude and phase related to the chromaticity of such article, second photoelectric means responsive to such collected light having the color of such first beam only, means to transmit a reference value of intensity-modulated light from such second beam to said second photoelectric means, whereby an alternating electric current is provided which has an amplitude and phase related to the brightness of such article, and classifying means comprising phase-sensitive rectifying means electronic switches responsive to each of said photoelectric means for classifying such articles into groups according to chromaticity and brightness classes corresponding to selected values of such electric currents.

Apparatus for classifying articles by color, comprising a light source which provides first and second light beams, a shutter for modulating the intensities of such light beams in phase opposition, an adjustable attenuator for adjusting the relative intensities of such light beams, said attenuator comprising a rotatable polarizing disk in the path of both beams and two polarizing disks arranged in the paths of respective ones of such beams, said two polarizing disks being oriented with their directions of polarization perpendicular to each other, different color filters positioned in the respective paths of the two beams, so that the beams have different colors after passing through the filters, means to direct the two colored beams to an article to be classifled, an integrating sphere arranged to collect substantially all light reflected by such article, first photoelectric means responsive to both colors of such collected light, whereby an alternating electric current is provided which has an amplitude and phase related to the chromaticity of such article, second photoelectric means responsive to such collected light having the color of such first beam only, means including another adjustable attenuator and a light-transmitting tube for transmitting a reference value of intencity-modulated light from such second beam to said second photoelectric means, whereby an alternating electric current is provided which has an amplitude and phase related to the brightness of such article, and classifying means comprising phase-sensitive rectifying means and electronic switches for classifying articles into groups according to chromaticity and brightness classes corresponding to selected values of such electric currents.

5. Apparatus for classifying articles by color, comprising a light source which provides first and second light beams, a shutter for modulating the intensities of such light beams in phase opposition, an attenuator for adjusting the relative intensities of such light beams, color filters positioned in the two beams to transmit different colors in the respective beams, means to direct the two colored light beams to an article to be classified, an integratin sphere to collect light reflected by such article, first photoelectric means responsive to both colors of such reflected light, whereby an alternating electric current is provided which has an amplitude and phase re- 8 lated to the chromaticity of such article, second. photoelectric means responsive to such reflected light having the color of such first beam only, means to transmit a reference value of intensitymodulated light from such second beam to said second photoelectric means, whereby an alternating electric current is provided which has an amplitude and phase related to the brightness of such article, and classifying means comprising first and second phase-sensitive rectifier bridges, first, second and third transformers each having a primary winding and a center-tapped secondary winding, the secondary winding of said first transformer being connected across opposite corners of both of said bridges, the secondary windings of said second and third transformers being connected across the other corners of said first and second bridges respectively, means for energizing the primary winding of said first transformer by an alternating voltage synchronized with said shutter, circuit means for energizing the primary winding of said second transformer by said alternating current which is related to the chromaticity of such article, circuit means for energizing the primary winding of said third transformer by said alternating current which is related to the brightness of such article, a ground connection to the secondary windnig center tap of said first transformer, a first plurality of electron discharge devices each having a cathode, a control electrode and an anode, means for maintaining the respective cathodes of said first plurality of discharge devices at different electric potentials with respect to ground, the control electrodes of said first plurality of discharge devices being connected to the secondary winding center tap of said second transformer, a second plurality of electron discharge devices each having a cathode, a con trol electrode and an anode, means for maintaining the respective cathodes of said second plurality of discharge devices at different electric potentials with respect to ground, the control electrodes of said second plurality of discharge devices being connected to the secondary winding center tap of said third transformer, and; a plurality of relays connected to respective anodes of said discharge devices.

6. Apparatus for classifying articles by color comprising means to provide two light beams of different colors, means to direct such beams to an article to be classified, means for modulating the intensities of such beams in phase opposition, photoelectric means responsive to both colors: of light reflected by the article for deriving an alternating electric signal related to the chromaticity of the article, additional photoelectric means responsive to only one color of light refiected by the article for deriving an electric signal related to the brightness of the article, and means responsive to electric signals produced by both, of said photoelectric means for producing an indication of the color and brightness classifiication of the article.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,066,934 Gulliksen Jan. 5, 1937 2,114,867 Wilson Apr. 19, 1938 2,162,529 Dawson et a1. June 13, 1939 2,183,606 Day Dec. 19, 1939 2,244,826 Cox June 10, 1941 2,316,375 Van Hoften Apr. 13, 1943 

